Microsoft Corp. illegally took technology used to link spreadsheet data between two of its programs from a Guatemalan inventor, lawyers said during opening statements at a jury trial that started on Tuesday.

Carlos Armando Amado said in a lawsuit that he filed for a patent in 1990 for software that links Microsoft's Excel program with its Access database application via a single spreadsheet, and that he unsuccessfully tried to sell it to Microsoft two years later.

Amado is seeking damages that could exceed $500 million in in the lawsuit filed in the U.S. District Court of Central California.

Microsoft, based in Redmond, Washington, began using his software without permission in various versions of Access, such as Access 95, 97, 2000 and 2002, according to Amado, who said he created the technology while he was a graduate student at Stanford University.

The suit did not specify a figure for damages, but Amado's attorneys estimated that it was about $2 per software copy sold, which would equal about half a billion dollars based on the software sold to date.

Joel Freed, Microsoft's attorney, disputed Amado's claims, saying Microsoft started working on such technology in 1989, three years before Amado approached the software giant with his idea.

At issue is a technology that allows computer users to transfer data back and forth between Excel and Access by using a spreadsheet.

Freed said the plaintiff had recreated the data transfer for the courtroom. "It's never happened with anyone outside this courtroom," he said.

Microsoft spokeswoman Stacy Drake said the company currently has about 35 other patent infringement suits pending.